Burkert Type 1094 - Manual (Page 7)

1094 - 5
english
2 SYSTEM DESCRIPTION
2.1 General description ot the area of use
When refuelling a vehicle, the petrol flowing into the fuel tank displaces an equal
volume of petrol vapour out of the tank. In order to prevent this petrol vapour from
escaping into the atmosphere, it must be sucked away.
In the solution offered by Bürkert, this suction process takes place by means of
underpressure via a proportional valve mounted in front of the reservoir tank of the
fuel pump. A suction pump transports the petrol vapour out of the vehicle tank and
presses it into the reservoir tank of the petrol pump.
To avoid excessive pressure in the reservoir tank, the volumetric pressure between the
petrol being delivered and the returned petrol vapour must be balanced.
The amount of petrol filled into the vehicle tank is measured using a calibrated piston
meter in the petrol pump, is converted into pulsed signals by the petrol pump compu-
ter and is reported to the controller.
2.2 Method of operation of the controller
The controller shown on Figure 1 evaluates the pulsed signals from the petrol pump
computer and, by means of electrical PWM control signals, controls the area of flow
of a control valve (explosion-protected proportional valve of Type 2832) and thereby
the flow rate of the returned petrol vapour.
Figure 1: Electronic controller Type 1094 Standard